1. Technical Field
The invention relates to a weight compensation device for a lifting door, in particular for a high-speed industrial door, having a spring element, a tensile element and a winding device, wherein one end of the spring element can be secured to the floor, wherein the tensile element is attached by one end to the spring element and by the other end to the winding device, wherein the winding device can be coupled to a drive of the lifting door, and wherein the tensile element can be wound onto the winding device or unwound from it in such a way that the spring element has its maximum prestress when a door leaf of the lifting door is in the closed position, and is essentially relieved of stress when the door leaf is in the open position.
2. Related Art
In order to balance the weight of a door leaf of a lifting door it is known to provide weight compensation devices. These typically have spring elements which are under maximum prestress when the door is closed and therefore assist the opening movement of the door leaf. However, this not only results in a reduction in the necessary drive torques when such a lifting door is actuated but also, given the correct adjustment of the arrangement, prevents sudden dropping of the door leaf in the event of a fault.
For this purpose, the prestressing force of the spring element is selected such that it exceeds the respective weight of the free length of the door leaf, that is to say of the door leaf section which is not moved out of the door opening, up to a desired balance point in all cases. In modern industrial doors, this balance point is typically at a door opening height of 2.5 m. In other words, the door leaf moves automatically as far as an opening position with a passage height of 2.5 m if, owing to a defect in the drive mechanism or due to manual release, for example in the case of a power failure, a blocking effect is no longer provided by the drive.
In lifting doors with relatively low power requirements it is known in this context, for example, to use torsion springs for the weight compensation. Said springs are arranged coaxially with respect to a drive shaft and are completely stressed in the closed position of the door leaf and correspondingly relieved of stress when the door leaf is opened. However, such torsion springs are subject to increased wear, for which reason their service life is limited. In particular when there is a frequent and sudden reversal of direction of the movement sequence of the lifting door such torsion springs are subject to considerable dynamic tension peaks owing to the jolting movements.
Therefore, weight compensation devices of a design such as is explained, for example, in WO 91/18178 have gained a widespread acceptance for such application purposes and in particular in high-speed industrial doors. Said weight compensation devices have a spring element, typically a helical spring, and a tensile element which is attached thereto and is generally in the form of a belt. The lower end of the spring element is fixedly connected to the floor here while its upper end is coupled by the tensile element to a winding shaft which is arranged at the lintel side of the lifting door. The tensile element is wound up onto this winding shaft here in the course of the closing process of the lifting door, and is wound up with layers which rest directly one on the other so that the spring element is increasingly stressed. On the other hand, the opening movement of the door leaf is associated with an unwinding process of the tensile element from the winding shaft so that in this context the spring element is relieved of stress. The winding shaft is coupled to the drive of the lifting door here.
This method of weight compensation has also proven itself because it results in the characteristic of the weight compensation process being adjusted to a satisfactory degree. While the gravitational force of the door leaf section which is located in the plane of the door in the course of an opening movement or closing movement changes essentially linearly as a function of the progress of the movement, the spring element for this known weight compensation device does not typically exhibit a linear characteristic curve profile. In order, on the one hand, to keep the necessary engine torques low here and, on the other hand, nevertheless to produce the desired balance point at, for example, a height of 2.5 m, structural adaptation of various parameters such as the selection of the core diameter of the winding shaft, the thickness of the tensile element and the length at rest and spring strength of the spring element is possible depending on the type of door leaf and the predefined door height. In view of the large number of different dimensions of lifting doors which are applied in practice and the types of door leaves which are available for said doors, such as flexible curtains, slatted armor etc., a considerable degree of expenditure is therefore necessary in order to make available a suitably dimensioned weight compensation means for each door system.
In addition, in modern high-speed industrial roller doors such as are described, for example, in DE 40 15 215 A1, DE 199 15 376 A1 and DE 102 36 648 A1, door leaves are guided in lateral guide rails in such a way that when the lifting door is opened they are accommodated in a contact free manner in the lintel area of the door opening. Such a configuration generally requires comparatively few rotations of the drive shaft so that also only a relatively small number of revolutions are available for the conventionally used winding shaft for the tensile element of the weight compensation device. Conventionally, in order to achieve the desired prestressing force of the spring element it is therefore frequently necessary to accept the expenditure on structural adaptations such as, for example, an additionally arranged speed-changing transmission mechanism.